In the case where the weight of an object such as, for example, a metered and packaged product, is to be examined, a weighing apparatus is generally used wherein a weighing belt conveyor is loaded on a load cell which is a weight detecting means. While a delivery belt conveyor is arranged on one side of the weighing belt conveyor and a discharge belt conveyor is arranged on the other side of the weighing belt conveyor, the packaged product is delivered onto the weighing belt conveyor and the packaged product of which weight has been measured is subsequently discharged onto the discharge belt conveyor and, if necessary, a sorting device is operated.
However, since this type of weighing apparatus is designed to measure the weight of the object to be weighed during a movement of the object by means of the weighing belt conveyor as described hereinabove, the object tends to receive an aerodynamic force such as a buoyance generated as a result of a difference in speed between the object being moved and air surrounding the object, resulting in a measurement error. Specifically, as the speed of transport of the weighing belt conveyor increases, the measurement error tends to become large.
As a countermeasure, there has been proposed a method of measuring respective weights of a sample of the object held in a stationary state and also in a state of being moved, and then correcting at a data level a measurement error which would occur during the movement of the object to be actually weighed. However, if the shape of a package of the object and/or the interval between the successively transported objects vary, a change may occur in the flow of air and, for this reason, the magnitude of an aerodynamic force varies accordingly. Consequently, there has been a problem in that a measurement error occurs.
Also, for minimizing the difference in speed between the object to be weighed and the air around the object, a method has been proposed wherein air is blown in a direction conforming to the direction of transportation of the object to be weighed. However, this method has a problem in that, since it is extremely difficult to make the flow of the air uniform, a wind pressure may act on the object being weighed and/or the weighing belt conveyor, resulting in a varying result of measurement.
The present invention has been devised with due regards paid to those problems and is intended to provide a weighing method of and a weighing apparatus wherein, regardless of the speed of transportation of the weighing belt conveyor, the size of the object to be weighed and the shape of the package, any possible measurement error attributable to the aerodynamic force such as the buoyance generated during the transportation can be minimized.